Stencil sheet



15 stylo. Such sheets are used on the duplicating Patented Dec. 2o, 1931.. l '2,140,506

p UNITED STATES PATENT ol-Flcs s'rENcn. SHEET Charles V. Canning, New York, N. Y., assigner to Sweets laboratories, Inc., New York, N. Y., a corporation of New York Application September 29, 1932, Serial No.' 635,428

8 Claims. (Cl. i1-38.6)

' The present invention relates to stencil sheets, Another formula for a' coating composition for and has for its object to produce a stencil sheet this purpose, which has been found to be highly which shall be durable; capable of giving sharp satisfactory is the followingzimpressions, when used on duplicating machines, Per cent and which will remain unaltered in storage for a Gum chicle 50 5 long time, and will be economical to manufac- Unvulcanized rubber.. ture and convenient to use.` Paraln wax Sheets are well known, for use as stencil sheets, Coumarone `resin 10 which have as a base a sheet of relatively porous In the mst formula instead of the unvulcamzed 10 strong paper Such as Yoshmo paper havmg a' rubber, it is possible to also employ other rubbery coating which is readily perforated by means of materials v, preferably in an unvulcamzed condithe type of a typewriter (the ribben usually bemg tion. In place of the coumarone resin above repulled back out of the way'during such operation) ferred to, other resins (natural or Synthetic) and also Whlch Wm be perforated by means ef a' can sometimes be substituted for' all or a. portion of the coumarone resin. Resinous rubbers such as Pontianak can be used, in place of some or all Y of the coumarone resin. I have in the first above Jeet matter of Whleh comes may be deemed formula used two diiierent grades of coumarone In accordance with the present invention I i 1 hh m int u have found that highly suitable stencil sheets may gsngnl' ger leireofn ich 20 `be prepared from paper such as Yoshino or other 10W-er melting point. say 63.. C It Wm be under paper of similar eharaeteriseies by coating the stood that various blends of hard and soft cou;- same on one or both sides with a composition marone resin with or Without various other, containing rubber, coumarone resin and a mineral resins can be employed or a resin having an im' or other ou aetmg as e' softening agent' The termediate melting point. Such materialsand 25 proportions eethe materials to be employed can mixtures are hereinafter included in the term be vened eensldere'bly but thefenewmg proper" resin. In some cases it is advisable to also add tions have been found in practice to be very 5 machine such as the Neostyleand others, for producing many copies of a letter, or other subt. f to A to the rst formula, a. small proportion of a wax sa 1S ac ry Per cent such as beeswax, paraiilne wax, Japan wax or a 'Rubber (unvulcamzed) 28.5 mixture of these. Stearin o1 other fats can also 30 be used, and liquid fatty oils'can be used. The

geumerene ge degrees eeittgrede-"f 6g latter can replace the mineral oil used in the'above Mciraa'o A degrees een erede-" 2 5 formula, and the waxes and fats can be substituted for a part of the coumarone resin, for ex- Ihe above composition can be dissolved in a. suitample canbe substituted for the low melting point 35 able solvent, and any desired coloring matter can coumarone resin referred to in the above formula. be added to the solution or to the material before These substances like the mineral Oil, HJSO act as dissolving the some in the solvent, after which softening agents, and are hereinafter included in. the paper may be dipped into the solution or the term softener.

40 contacted with the upper surface of the solution In the second formula, also, the substitutions 40 in such a way as to coat one side only of the as referred to, can be made. It is also possible paper with the solution. Then the solvent is t0 use rubber? material Which also Contains a evaporated, leaving the mixture consisting essenconsiderable amount of resins, (as a substitute for tially of rubber, coumarone resin and mineral oil, the resin and a part 0f the rubber). for example nrmly adheringto the paper. Such a, sheetmay Pontianak or Jelutcng. Paraftln wax is men- 45 be applied in the usual manner -to the backings tioned in this formula. In place of all or part which are commonly used in the art, and will be? of the same, I Can emPlOY hard fifi-110W, hard found tofhave the desired degree of flexibility and hydrogenated oil. The term Oily material" 1S the properties above referred to. The oil used on intended to include such substances. In Place 0f this formula. may be a high viscosity lubricating the Kcoumarone resin, various other synthetic 50 oil, e. g. automobile motor oil. resins and/or natural resins, or mixtures'thereof -In some cases it may be advisable to coat the can be used. Various inks or dyes or coloring paper on both sides with the said composition, agents can beadded to either of these formulas. and the coating on the reverse side being very Pontianak and Jelutong are rubbery materials 55 thin. Usually coating on one side is better. from certain shrubs growing in Borneo, Malay 65 Peninsula and Sarawak, and these contain very large percentages '(75 to 85%) of natural resins, and small amounts (l-20% or so) of rubber (on the dry basis). 'I'hey may containi, in their. crude state, as imported, substantial percentages of water, and the said materials are both subject to fermentation.

The solvents applicable `for this purpose are carbon tetrachloride or ethylene dichloride or similar rubber solvents, ethylene dichloride being recommended due to the fact that the ink coloring used is dissolved morey satisfactorily in it. The proportions may be approximately 3 or 4 parts of solvents to one part of composition.

The coating ofboth sides of the sheet is not necessary nor generally advisable as it would be apt to make the iinished stencil hard to cut through. Furthermore, coating on one side is all that is necessary to make a satisfactory stencil.

The rubber can be first roll-milled for to`30 minutes more or less. Then the coumarone resin is blended into the rubber, which can conveniently be done on the roller mill. This mixture can then be incorporated with the other ingredients, either on a roller mill or in a steam-heated mixing kettle having stirring arms or paddles. The partial breaking down of the rubber, as produced on the roller mill, considerably improves ther consistency oi' the mass. The ink or color can be added in the mixing kettle, and obviously any desired color can be employed.

It will be understood that one company may I make u p and sell the compositions, (with or without the solvent and/or color) and the coating operation (with or-without disssolving the composition in a solvent and adding the color) can be performed by another company.

In the annexed drawing I have shown diagrammatically sections of three modifications. In Fig. 1 is shown paper carrying the composition on one side only (and naturally the paper will be itself impregnated with the composition). In Fig. 2, I have shown the coating applied to both sides of the paper, the coating on one side here represented as the top being thick, Whereas the coating on the other side (here represented as the bottom) being shown thin. Fig. 3 is another modification, as in the second example given.

I am aware that heretofore-it has been pro- 0 posed to employ proteins (including gelatin and or glue.

1. A stencil sheet comprising a paper sheet, carrying a. composition comprising unvulcanized rubber, coumarone resin and an oil which will act as a softening agent for such composition.

2. A stencil sheet which consists of paper coated with a composition comprising rubber, high melting point coumarone resin, low melting point coumarone resinjand mineral oil.

3. A stencil sheet which consists of paper coated with a composition comprising about 28.5 parts of unvuicanized rubber, about 60 parts of high melting point coumarone resin, about 9 parts of low melting point coumarone resin and about 2.5 parts of mineral oil.

4. A stencil sheet coated with a composition which consists essentially of Aplastic non-brittle material selected from the group consisting of rubber and resinous rubber, wax and resin.

5. A stencil sheet coated with a composition which consists lessentially of a blend of chicle,`

rubber and resin, with an oily material.

` 6. A stencil sheet coated withr a composition which is composed essentially of a blend of a plastic non-brittle' material selected from the group consisting ofrubber and resinous rubber, a resin and a softener.

7. A stencil sheet coated with a compositionv which is composed essentially of a blend of a plastic non-brittle material selected from the group consisting of rubber and resinous rubber, a resin and an oily material to act as a softeningagent. l l

8. A stencilsheet coated with a composition which is composed essentially of a blend of a plastic non-brittle material selected from the group consisting of rubber and resinous rubber, a resin and a wax to act as a softening agent.'

` CHARLES V. CANNING. 

